Merci les gars de vous intéresser au sujet !
J'ai fait un peu de recherche hier sur google en regardant les images de tuners de S1 de fin des années 20 et je suis tombé sur ce topic initié par Winin Boy :
https://umgf.com/info-on-uke-tuners-t103773.html(on y voit pas les tuners en question car le topic est vieux et l'image a sauté du forum, par contre elle avait été gardé en mémoire par Google et j'ai donc pu remonter à la source)

ça y ressemble pas mal je trouve !
et donc un gars a répondu :
These tuners are definitely period. Versions of these tuners date back to the 1880s, but I'm not sure when they were first made specifically for ukuleles. These were referred to as "Champion Key" tuners. I don't think they were originally (in the early 1920s) a Grover product, but I do agree that later Grover took up the Champion line and produced a very similar tuner. John King pointed out the patent on these tuners to me, and included it in his book about ukulele Patents and Trademarks. Here are some photos...
As for Martin, in November of 1920 their expense book lists a purchase of "100 Champion Keys, White, Ukulele" at 14 cents each. This was the earliest purchase I could locate. Martin charged dealers extra when they requested these patent pegs. However, I don't recall seeing any Ditson orders where special pegs were specified (or charged). I believe that the Ditson NYC store was probably putting these on their ukuleles themselves after receiving them from Martin. My two Ditson dreadnought ukuleles both have this style of peg. I'm not sure if Grover eventually purchased the rights from Filstrup, or if they just took up a very similar design.
Et Winin Boy qui dit plus loin :
Anyhow, this is why I personally have always dated the Martins that are (originally) fitted with those classic Grover barrel pegs to some time between 1924-1927 - incidentally Martin's most productive ukulele building years. Which would explain why we still see them so very often.
==> je suis pas sûr d'avoir tout compris dans la discussion, mais j'ai pas trop de doute sur l'authenticité des tuners, pour moi ça match à priori
